Add a 'bool TryGetSystem()' method to SystemClass
Add a 'bool TryGetSystem()' method to SystemClass

This is a basic public wrapper that combines GetSystem with a new
(private) SystemAliases DB table lookup method.

Accessibile underpinnings for feature #713.

jgoode/EDDiscovery,jthorpe4/EDDiscovery,mwerle/EDDiscovery,jgoode/EDDiscovery,mwerle/EDDiscovery